1. Field of the Invention
This invention relates to a robot controller of a robot system which conducts force control by using a three-axial force sensor that measures three components consisting of a force in one axial direction and moments about the axes in two axial directions that are at right angles with the above axis and are, further, at right angles with each other.
2. Description of the Related Art
A three-axial force sensor has been known which is capable of measuring three components consisting of a force in one axial direction and moments about the axes in two axial directions that are at right angles with the above axis and are, further, at right angles with each other. As disclosed in Japanese Unexamined Patent Publication No. 2010-112864, the above three-axial force sensor is small, can be inexpensively produced, and is widely used.
The axis in which the force is detected by the three-axial force sensor 3 is presumed to be the Z-axis, and the axes that are at right angles with the above axis and are, further, at right angles with each other are presumed to be X-axis and Y-axis, respectively. Further, the forces acting in the directions of X-axis, Y-axis and Z-axis are denoted by Fx, Fy and Fz, and the moments acting about the X-axis, Y-axis and Z-axis are denoted by Mx, My and Mz, respectively.
Japanese Unexamined Patent Publication No. 2010-112864 discloses a five-axial force sensor which includes a first measuring unit for detecting three components consisting of the force Fz and the moments Mx and My, and a second measuring unit for detecting two components consisting of the forces Fx and Fy. The five-axial force sensor is small and is capable of directly sensing translational forces Fx, Fy and Fz in the directions of a plurality of axes and moments Mx and My about the X- and Y-axes.
However, the five-axial force sensor that includes the second measuring unit for measuring the forces Fx, Fy disclosed in Japanese Unexamined Patent Publication No. 2010-112864, is produced and calibrated requiring a lot of laborious work and time.
Further, the conventional three-axial force sensor for detecting the three components of force Fz and moments Mx, My is capable of executing no more than the force controlling by using these three components, such as controlling the force in the direction of Z-axis, controlling the torque about the X- and Y-axes, or controlling the posture to align the faces about the X- and Y-axes. Therefore, it is difficult to cope with a complex control which requires four or more components.
The present invention was accomplished in view of the above-mentioned circumstances and has an object of providing a robot controller which, despite of using the three-axial force sensor, presumes the forces and moments that could not be detected by the three-axial force sensor in order to control the forces like when a six-axial force sensor is used.